Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$191.71	11.329%	$213.4288	$213.43	$213.45	$213.40
Purchase #2	$241.38	7.606%	$259.7394	$259.74	$259.75	$259.70
Purchase #3	$40.90	4.832%	$42.8763	$42.88	$42.90	$42.90
Purchase #4	$38.48	6.852%	$41.1166	$41.12	$41.10	$41.10
Purchase #5	$160.81	7.868%	$173.4625	$173.46	$173.45	$173.50
Purchase #6	$31.93	3.482%	$33.0418	$33.04	$33.05	$33.00
Purchase #7	$215.71	9.767%	$236.7784	$236.78	$236.80	$236.80
7 purchase totals =	$920.92		$1,000.4438	$1,000.45	$1,000.50	$1,000.40